Polyester based fibers comprising a non-linear branched ethylene terephthalate polymers

ABSTRACT

THIS INVENTION PROVIDES NOVEL POLYESTER FIBERS WHICH WHEN FORMED INTO A FABRIC DO NOT GIVE RISE TO PILLING OR FIBRILATION, MADE BY MELT-SPINNING BRANCHED CHAIN POLY-   ETHYLENE TEREPHTHALATE OF SPECIFIED VISCOSITY CHARACTERISTICS, AND HAVING SPECIFIED TENSILE STRENGTH.

April 21;'1911 Y VAQNAY' 3,516,113

POLYESTER BASED FIBERS IOMPRISING A NON-PLINAR BRANCHED ETHYLENE TEREPHTHALATE POLYMERS Filed June 5. 1969 ,QQ/tex Y Inventor Yves Vagina):

B Chmmzy@ ash/mf tlarncy United States Patent Oi Int. cl. cosg 17/04 U.S. Cl. 260--22 3 Claims ABSTRACT OF THE DISCLOSURE This invention provides novel polyester fibers which when formed into a fabric do not give rise to pilling or fibrillation, made by melt-spinning branched chain polyethylene terephthalate of specified viscosity characteristics, and having specified tensile strength.

This invention relates to polyester fibers and a process for their preparation.

Fabrics woven from yarns of polyester fibers derived from terephthalic acid and ethylene glycol have exceptional strength, abrasion resistance and pleat retention. However the development of the use of polyester fibers in loosely woven or knitted fabrics is restricted to a large extent by the problem of pilling. In fact, in these types of fabric the individual fibers tend to migrate towards the surface and to form fibrous globules or pills which cannot become detached because of the high abrasion resistance and tensile strength of the polyester, i.e. the rubbing forces are much lower than the force required to tear the polyester fibers holding the pill.

As it is very difiicult to prevent migration of the fibers attempts have been made to lower the mechanical properties of the polyester fibers and to adapt their tensile strength to the rubber forces applied during normal wear. During wear, the abrasion progressively lowers the tensile ystrength until it corresponds to the rubbing forces and pill drops off.

It has been attempted to lower the mechanical properties of the polyester fibers using polymers of lower molecular weight. Unfortunately the reduction in the molecular Weight of the polyester is accompanied by a reduction in the viscosity in the fused state and in industry it is very difficult to spin a polyester having a viscosity in the fused state at 285 C. of less than 600 poises without the fibers sticking together. It is therefore difficult to obtain a fiber suitable for normal commercial use.

Although many attempts have been made to lower the tensile strength by treating the yarn or the woven fabric they have always come up against practically insoluble problems of reproducibility.

The present invention provides oriented polyethylene terephthalate fibers which are easily accessible industrially and yarns of fibers which do not give rise to pilling. Accordingly this invention provides a polyester-based fiber having an elongation at break of greater than and a tensile strength of 18 to 36 g./tex which comprises a branched polyethylene terephthalate having a specific viscosity of 0.47 to 0.72 and a melt viscosity of 600 to 2500 poises at 285 C.

The fibers of this invention may be used in the manufacture of woven or knitted fabrics which substantially do not form pills.

For woven fabrics fibers having a tensile strength of 26 to 36 g./tex and for knitted fabrics fibers of 18 to 25 g./tex are generally chosen.

Depending on the proposed use and on any fibers with 3,576,773 Patented Apr. 27, 1971 ice which they are mixed, the elongation of the fibers of this invention may vary within wide limits. When they are used in admixture with wool and cotton, fibers having elongations of 25 to 60% are chosen.

The products of this invention shown very slight variations in tensile strength with elongation for a constant specic viscosity and a constant melt viscosity consequently the graph of the variation in tenacity with specific viscosity can be accurately constructed, taking into account the scatter in elongations normally observed in industrial production.

The other characteristics of the fibers of this invention are interdependent. For example, for an elongation of 35% the points representing fibres of this invention are loca-ted within the area ABCD of FIG. l of the accompanying drawing. On this diagram the segment AB corresponds to the polymers having a viscosity 600 poises and the segment DC to the polymers having a viscosity 2,500 poises. The fibers currently sold commercially correspond to points above the segment BC.

The fibers of this invention may be prepared by extruding, in the fused state a branched polyethylene tercphthalate containing y/ 11;-2 to z/ n-Z equivalent percent of n-valent chain units where n is 3 or 4, y is 0.2 and z is 2 having a specific viscosity of 0.47 to 0.72 and a melt viscosity of 600 to 2500 poises and orienting the yarns thus obtained by stretching.

The polymers used to prepare the products of this in- 'vention are branched polyethylene terephthalates and may be prepared by incorporating a branching agent, having three or four groups capable of forming stable bonds, such as ester, ether or amide bonds with the acid or alcohol groups, into the monomer mixture.

The preferred branching agents are polyols such as trimethylolpropane, trimethylolethane, pentaerythritol or glycerine; polyacids such as trimesic acid, trimellitic acid or anhydride or pyromellitic acid or anhydride; polyphenols such as phloroglucinol or hydroxyhydroquinone; amino acids and acid-alcohols such as hydroxyisophthalic acid or aminophthalic acid; 2,2-bis(4epoxypropoxyphenyl) -propane or diethanolamine.

Depending ou the method of polyester synthesis employed 0.2 to 2 mols percent of the trifunctonal branching agent relative to the terephthalic acid, or the terephthalic acid derivative, `are used. Amounts of the order of 0.1 to 1 mol percent are preferred.

The polyesters which may be used in the process of this invention are essentially derived from terephthalic acid, ethylene glycol and a branching agent. They can however contain a proportion, up to 10 mol percent, of another glycol containing an aliphatic, cycloaliphatic or aromatic group or hetero-atoms such as propanediol, butanediol, hexanediol, decanediol, dimethylpropanediol, cyclohexanedimethanol, cyclobutanedimethanol, xylylene glycol, polyoxyethylene Iglycol of molecular weight less than 6,000, polytetrahydrofuran, another diacid such as adipic, sebacic, dodecanedioic, isophthalic or hexahydroor terephthalic acid, or dimeric acids derived from linoleic acid.

These polymers are preferaably prepared in the presence of the usual transesterification and polycondensation catalysts and may contain agents to improve their colour or heat stability such as phosphorus derivatives e.g. phosphorous acid, phosphoric acid, phenylphosphonic acid or triphenylphosphite. They can also be matted, for example by adding a suspension of titanium oxide.

The following examples illustrate this invention. In these examples the terms used have the following meanings:

Specific viscosity: the specific viscosity kat 25 C. of therpolyester as a 1% solution in ortho-chlorophenol;

Melt viscosity: the viscosity in poises of the fused mass measured at 285 C.;

Pilling: the pilling observed after 30 minutes of the so-called Random Tumble Pilling Test or RTPT (Standard Specification ASTM D 1,375-64), the index l 4 so as to form a yarn of 40/1 count and with a right-hand twist of 630 (coefficient of twist 100), and this yarn is then woven into a twill fabric. The woven fabric is desized, heat-set, dyed in the presence of a carrier, singed, brushed and cropped in accordance with the usual processes.

being assigned to articles having large numbers of pills 5 When tested by the Random Tumble Pilling Test and index 5 to articles practically free from pills; (ASTM D 1,375-64) it gives an index of 5 after 30 Fibrillation: the observed elfect produced by abrasion minutes, that is to say there is practically no pilling on of dyed articles at the points of maximum rubbing. The the surface of the woven fabric. linear polyester fibers in fact have a tendency to split into It also possesses good pleat retention. fibrils when they are iirmly held in a tightly woven article A standard polyester having a specific viscosity of 0.57 and to show the undyed core of the polyester thus producand a melt viscosity of 600 poises is spun under the same ing a bleaching effect. conditions. A large amount of adhesion between filaments,

In the following examples, the pilling tests were carried causing stretching defects so that the cleanness of the out on fabrics of rather loose construction such as twill iinal fiber is very poor, is observed. or knitted fabrics, While the fibrillation test was carried out The properties of this ber are as follows: on fabrics of tight weave such as plain sheeting. Gauge 3 3 decitex EXAMPLE 1 Tensile strength-35 g./tex Elongation at break- 35% The following are introduced into a transesterication o apparatus equipped with a stirrer, a double heating jacket Shnnkage m Steam at 130 C 3'5 and a fractionation column: A twill fabric of the type described above woven from Parts this liber is tested by the RTPT test; an index of 2.5 Dimethyl terephthalate 1,150 indicating the presence of many pills is obtained. This Ethylene glycol 361 tendency to form pills for practical purposes can not Calcium acetate 0.805 be improved because the use of polymer or lower mo- Antimony oxide 0.110 lecular weight gives melt viscosities of less than 600 Trimethyl trimesate 1 9.5 poises, incompatible with good industrial spinning.

1I.e. 0.65 mol percent relative to mols of dimethyl terepli- EXAMPLE 2 malate The cable obtained after assembly in Example 1 is at 'hteenrgrrs Ifegoagielltaslsoon stretched such that. its elongation at break is 22%. Its anol ceases at 230 C., the excess glycol is distilled and the propertles are then' following are added to the reaction mixture: Gauge-32 decitex Parts 35 Tensile strength-28.5 g./tex Phosphorous acid 0,402 Elongation at break-22% Titanium oxide suspended in ethylene glycol 5.75 shrinkage iIl Steam at 130 C-1-5% The mixture is transferred to a polymerisation auto- It is mixed With W00] ih the proportions 0f 55/ 45 clave where the temperature is progressively raised to and a Yam 0f 40/2 count With a 475 fight-hand SimPie 270 C, while the pressure is reduced to 0 4 H11- of twist (coeicient of twist 75) anda600left-hand doubling mercury. The polymerisation is stopped when the power iWisi (coefficient 95) is Produced A Plain fabric iS absorbed in stirring of the autoclave corresponds to a Produced With this yard melt viscosity at 285 C. of 800 poises. The specific After heet setting this fabric is dyed a deep haVY viscosity of the polymer thus obtained is 0.55 and its meltbide ih the Presence 0f a carrier N0 hhliliatiOIl 0f this ing point is 261 C. plain fabric is observed on wear.

This polymer is spun at 278 C. through a spinneret on ffhe ciber hand Standard Polyester ihefs 0f SPewith 168 0.50 mm. diameter holes and the yarn is wound miic Viscosity 0-57: stretched t0 give al1 elongation at up at a speed of 900 meters per minute No adhesion be break of 22%, and converted to a fabric under the same tween the laments is Observed. conditions as above, show considerable bleaching at the After assembling several yarns, the cable is stretched at Points 0f maximum rubbing due to briilation- 100 meters per minute in a sizing bath heated to 70 C., EXAMPLE 3 EL; grrlvirr? of 4'03 and 1s then crlmped m a cnmpmg Mixtures as in Example 1 but containing 0.6-5 mol The cable is cut on a Converter type of apparatus into gllrsof glclsligeriliss rcliglglseg Elgin I lne e mm bers havmg the followmg properties are then spun as above and the libers, after being mixedI Gauge-3.3 decitex with wool under the conditions of Example l, are con- Tensile strength-25 g./tex verted into a twill fabric for measuring pilling and into Eloiigation at break-35% 60 a plain fabric for measuring the fibrillation. 'I'he results Shrinkage in steam at C.-2% obtained are shown in the table below:

Melt viscosity Tensile Elonga- Experiment Specific (poises at Gauge strength tion at Woven Pilling Number viscosity 285 C.) (deeitei') (g./tex) break fabric RTPT Fibrillation 1 0. 58 1,000 3.3 26.5 34 'rwill 5 Nil.

2 0. 5s 1,000 3.2 30 25 Piain 5 Practically 3 0. 66 2,000 3.3 30 37 Twill 4.5 NiiiL 4 0. es 2,500 3.2 31 ---do 4 Nil.

5 0.68 2,500 3.4 20.5 55 do 5 Nil.

This fiber is mixed with Wool in the following propor- In all cases the high melt viscosity permits excellent tions: spinning and good stretching to give a fiber which does not adhere and is very homogeneous. Percent Polyester 55 75 EXAMPLE 4 Wool 45 Polymers of different viscosities are prepared undei the conditions described in Example 1 but the trimethyl trimesate is replaced by 0.8 mol of trirnethylolpropane per hundred mols of dimethyl terephthalate. The polymers are tested as above, with the following results:

Thus, using a mixture of dimethyl terephthalate, ethylene glycol, calcium acetate and phosphorous acid as in Example l, and 0.008 part of antimony oxide, it is pos- Melt viscosity Tensile Elonga- Experiment Specific (poises at Gauge strength tion at Woven Pilling Number viscosity 285 C.) (deciter) (g./tex) break fabric RTPT Fibrillation 1 0. 57 1, 200 3. 3 25 39 TWilL 5 Nil.

2 0. 57 1, 200 3. 3 26. 5 24 PlaiL 5 Practically iiil. 3 0.62 2, 000 3. 4 27 34 Twill. 5 Nil. 4 0. 67 2, 500 3. 3 29 38 o 4. 5 Nil.

g./tex seems the lower limit of tensile strength for use industrially in the manufacture of woven fabrics.

EXAMPLE 5 The replacement of the 0.8 mol percent of trimethylolpropane used in Example 4 by 0.4 mol percent of pentaerythritol gives results similar to those of Example 4.

Melt viscosity Tensile Elongac Experiment Speelc (paises at Gauge strength tion at Woven Pilling l Number viscosity 285 C.) (decitex) (g.,/tex) break fabric RTPT Fibrillation 1 0.57 l, 250 3. 3 25. 5 33 Twill.. 5 Nil. 2 0.66 2, 500 3. 3 29 31 do 4. 5 Nil.

EXAMPLE 6 Polyethylene terephthalates are prepared with 0.38 mol percent of various trifunctional branching agents, and the following pilling results are obtained on a twill fabric prepared described in Example 1.

cosity at 285 C. 1,050 poises) is 1 hour 55 minutes, and

this ensures both good reproducibility between experiments and economical use of the apparatus.

This polymer is spun and stretched as in Example l and Melt Specific viscosity Gauge Tensile Ellonga- A t Experiment viscos- (poises at strength tion at Pilling` Number Branching agent ity C.) (g./x) break RTP'l 1 Glycerine 0. 54 630 28 37 5 2 Trimetliylolpropane 0. 54 600 3.3 27 40 4. 5 3 Methyl hydroxyisophthalate.. 0 54 650 3. 2 28 33 4. 5 4 Trimethyl trimesate 0. 54 60() 3. 3 2f) 35 4. 5 5.. Glycerine 0. 67 1. 850 3. 3 35 39 2.5 6.- 0. 67 l, 950 3. 2 36 32 2. 5 7 0. 67 1, 880 3. 4 35 35 3 The results are very similar regardless of the trifunc tional compound used which indicates that if the compound introduced forms stable bonds it is the branching of the polyester chains which affects the mechanical properties and not the manner of branching.

EXAMPLE 7 Similarly, polyesters containing 0.55 mol percent of trimethylolethane 4are used as above, with the following results:

Tensile Elonga- Experiment Specific Gauge strength tion at Pilling Number viscosity (decitcx) (g./tex) break RTPT EXAMPLE 8 then cut into 80 millimeter bers having the following properties:

Gauge-3.3 dtex Tensile strength-22 g./ tex Elongation at break-41% This fiber is mixed with wool in the proportion of 55/45 and a yarn of 36/1 count and 540 right-hand twist (coeicient 80) is prepared. This yarn is knitted, heat-set and then dyed with a carrier.

When subjected to the pilling test the knitted fabric has an index of 4, which is excellent for this type of article. If the knitted fabric is subjected to brushing and cropping the index is then 5.

A knitted fabric obtained from a yarn of 40/1 count and coeicient of twist of 85, in a polyester/ wool mixture in the proportion of 70/ 30, is rated as 3 in the same test, and as 4-5 after cropping and brushing.

A knitted fabric prepared from the standard polyester described in Example 1 and treated under the same conditions is rated as follows:

in a /45 mixture-index 1 in a 30 mixture-index 1 EXAMPLE 9 Three polyesters of different specific viscosities are prepared under the conditions described in Example 8 from a monomer mixture containing 1.2 mol percent of trimethylolpropane relative to the dimethyl terephthalate.

When treated as described in Example 8, the following results are obtained:

state at 285 C. of 1,500 poises is obtained. Its specific viscosity is then 0.60. When spun and stretched under It can be seen from these results that by using a polyester of low specific viscosity (0.49) but of suicient melt viscosity for good spinning 1,100 poises), when the polyester is mixed 55-45 with Wool, it is possible to obtain, an article which without brushing or cropping is satisfactory from the point of view of pilling.

EXAMPLE A polymer containing 1.6 equivalents of chain links derived from trimethylolpropane is prepared, spun, and knitted as above, and tested as a 70/ 30 mixture with wool.

the conditions described in Example 1, it has the following properties after being cut into 90 mm. fibers:

Gauge-3.3 dtex Tensile strength- 24 g./tex Elongation at break-% It is spun, as a 55/45 mixture with Wool, into 40/1 (count) and then woven into a twill fabric, and dyed in the piece, without a carrier, to give a deep shade. In the RTPT test the fabric gives an index of 5 after brushing and cropping.

Bushing Tensile and Experiment Specific Gauge strength Elongation cropping RTPT Number viscosity (decitex) (g./tex) at break treatment rating Using this proportion of crosslinking agent and a polymer of low viscosity, the 70/ 30 knitted fabric can be used without brushing or cropping.

EXAMPLE l 1 The polymer prepared in Example 8 is spun and stretched to give individual bers having the following properties:

Gauge-1.7 dtex Tensile strength-23 g./ tex Elongation at break- 29% Cutmm.

These fibers are mixed with cotton in the proportion of 75/25, spun into 50/1 (count) with an 850` righthand simple twist (coefficient 120) and woven in a taifeta weave. This taffeta is tested for pilling by the RTPT test. The following results were obtained.

Index After printing 3 After brushing, cropping and printing 5 Under the same conditions a standard polymer of specific viscosity of 0.57 gives a woven fabric of index l, which is very low.

EXAMPLE 12 The fiber of Example 11 is mixed with cotton in the proportion of 50/50 and spun into 501/ 1 (count) with a 915 right-hand twist (coefficient 130), and then knitted into gauge 20 interlock.

After heat-setting at 210 C. and bluing in a bath, the knitted fabric is RTP'I tested and rated at 4, which is acceptable for this type of article.

EXAMPLE 13 A polyester which is branched with 0.8 mol percent of trimethylolpropane and which contains 6% by weight of polyoxyethylene glycol is prepared under the conditions described in Example 1 until a viscosity in the fused A11 unbranched copolyester of the same specific viscosity has the following properties under the same conditions:

Gauge- 3.2 dtex Tensile strength-3,6 g./tex Elongation at break- 35% The pilling test on a woven fabric prepared from this fiber gives a rating of 2.

EXAMPLE 14 This same ber :mixed with wool 70/ 30 and spun into 36/1 (count) is knitted and RTPT tested after setting and dyeing.

Without cropping and brushing, the knitted fabric is rated: 3-4 After cropping and brushing, the knited fabric is rated:

We claim:

1. A polyester-'based fiber having an elongation at break greater than 15% and a tensile strength of 18 to 36 g./tex, which comprises a non-linear branched ethylene terephthalate polymer containing 0 to 10 mol percent of ester structural units other than ethylene terephthalate units and y/n-2 to Z/n-Z equivalents percent of n-valent chain links, where n is 3 or 4, y is 0.2 and Z is 2, the remainder being ethylene terephthalate units, the said polymer having a speci-o viscosity of 0.47 to 0.72 as determined in a 1% solution thereof in ortho-chlorophenol at 25 C., and a melt viscosity of 600 to 2500 poises =at 285 C.

2. A ber according to claim 1 Iwherein the ethylene terephthalate polymer contains up to l0 mol percent of propanediol, butanediol, hexanediol, decanediol, dimethyl-propanediol, cyclohexane, dimethanol, cyclobutanedimethanol, xylylene glycol, polyoxyethylene glycol of molecular weight less than 6000, polytetrahydrofuran, adipic acid, sebacic acid, dodecanedioic acid, isophthalic acid, hexahydroisophthalic acid, terephthalic acid, a

10 dimeric acid derived from linoleic acid or a mixture t FOREIGN PATENTS thereof.

3. A ber `according to claim 2 wherein the tereph- 745690 11/1966 Canada 26o-75 thalate polymer is branched With trimethylolpropane, tri- OTHER REFERENCES mcthylolethane, entaerythritol, glycerine, trimesic acid,

trimellitic acid, rimelltic anhydride, pyromellitic acid, 5 Youngson et 31': Journal Chemlcal Society June 1950 pyromellitic anhydride, phioroglucinol, hydroxyhydropp 1613-1622 quinone, hydroxyisophthaiic acid, aminophthalic acid, 2, 2-bis(4-epoXypropoxypheny1)-propane or diethanolamine. DONALD E' CZAIA Primary Examiner 10 R. W. GRIFFIN, Assistant Examiner References Clted UNITED STATES PATENTS U.S. Cl. XR.

3,033,827 5/1962 Kibler et al. 260--77 8-179; 260-75 3,446,758 5/1969 Wiener 260-2'3 3,446,766 5/1969 Taylor 26o-z2 15 

